Ikeda et al, (1997) Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry 22: 3339-3344 and Sato et al, (1995) Journal of the Chemical Society, Perkin Transactions 1, 14:1801-1809 and Sato et al, (1994) Heterocycles 37(1): 245-248 disclose 4′,5′-unsubstituted acyl pyrrolidine compounds useful as reagents in the regioselective synthesis of bridged azabicyclic compounds; no medical use was disclosed for the acyl pyrrolidine compounds.
Ikeda et al, (1996) Heterocycles 42(1): 155-158 and Confalone et al, (1988) Journal of Organic Chemistry 53(3): 482487 and De Martino et al, (1976) Farmaco, Ed. Sci. 31(11): 785-790 disclose 4′,5′-unsubstituted acyl pyrrolidine compounds useful as reagents in the synthesis of tricyclic nitrogen-containing heterocycles; no medical use was disclosed for the acyl pyrrolidine compounds. Alig et al, (1992) Journal of Medicinal Chemistry 35(23): 4393-4407 discloses a 4′,5′-unsubstituted acyl pyrrolidine compound useful as a reagent in the synthesis of non-peptide fibrinogen receptor antagonists; no medical use was disclosed for the acyl pyrrolidine compound.
Padwa et al, (1992) Journal of the American Chemical society 114(2): 593-601 discloses a 4′,5′-unsubstituted acyl pyrrolidine compound useful as a reagent in the synthesis of azomethine ylides; no medical use was disclosed for the acyl pyrrolidine compound. Culbertson et al, (1990) Journal of Medicinal Chemistry 33(8): 2270-2275 and Crooks et al, (1979) Journal of the Chemical Society, Perkins Transactions 1, 11: 2719-2726 disclose 4′,5′-unsubstituted acyl pyrrolidine compounds useful as reagents in the synthesis of 7-spiroamine quinolone and spiro[indan-2,2′-pyrrolidine] compounds respectively; no medical use was disclosed for the acyl pyrrolidine compounds.
WO2002/44168, WO96/33170 and EP505868A2 disclose 4′,5′-unsubstituted acyl pyrrolidine compounds useful as intermediates in the synthesis of indolecarboxamide, N-aroylamino acid amide and N-acyl-α-amino acid derivatives respectively; no medical use was disclosed for the acyl pyrrolidine compounds.
De Caprariis et al, (1989) Journal of Heterocyclic Chemistry 26(4): 1023-1027 discloses 3 pyrrolidinedicarboxylic acid derivatives useful as intermediates in the synthesis of pyrrolo[1,4]benzodiazepine compounds; no medical use was disclosed for the pyrrolidinedicarboxylic acid derivatives.
WO99/37304 discloses oxoazaheterocyclyl derivatives, especially piperazinone compounds, having Factor Xa inhibitory activity. These derivatives may include certain acyl pyrrolidine derivatives. There is no mention of HCV polymerase inhibitory activity for the disclosed compounds.
Infection with HCV is a major cause of human liver disease throughout the world. In the US, an estimated 4.5 million Americans are chronically infected with HCV. Although only 30% of acute infections are symptomatic, greater than 85% of infected individuals develop chronic, persistent infection. Treatment costs for HCV infection have been estimated at $5.46 billion for the US in 1997. Worldwide over 200 million people are estimated to be infected chronically. HCV infection is responsible for 40-60% of all chronic liver disease and 30% of all liver transplants. Chronic HCV infection accounts for 30% of all cirrhosis, end-stage liver disease, and liver cancer in the U.S. The CDC estimates that the number of deaths due to HCV will minimally increase to 38,000/year by the year 2010.
Due to the high degree of variability in the viral surface antigens, existence of multiple viral genotypes, and demonstrated specificity of immunity, the development of a successful vaccine in the near future is unlikely. Alpha-interferon (alone or in combination with ribavirin) has been widely used since its approval for treatment of chronic HCV infection. However, adverse side effects are commonly associated with this treatment: flu-like symptoms, leukopenia, thrombocytopenia, depression from interferon, as well as anemia induced by ribavirin (Lindsay, K. L. (1997) Hepatology 26 (suppl 1): 71S-77S). This therapy remains less effective against infections caused by HCV genotype 1 (which constitutes ˜75% of all HCV infections in the developed markets) compared to infections caused by the other 5 major HCV genotypes. Unfortunately, only ˜50-80% of the patients respond to this treatment (measured by a reduction in serum HCV RNA levels and normalization of liver enzymes) and, of those treated, 50-70% relapse within 6 months of cessation of treatment. Recently, with the introduction of pegylated interferon, both initial and sustained response rates have improved substantially, and combination treatment of Peg-IFN with ribavirin constitutes the gold standard for therapy. However, the side effects associated with combination therapy and the impaired response in patients with genotype 1 present opportunities for improvement in the management of this disease.
First identified by molecular cloning in 1989 (Choo, Q-L et al (1989) Science 244:359-362), hepatitis C virus (HCV) is now widely accepted as the most common causative agent of post-transfusion non A, non-B hepatitis (NANBH) (Kuo, G et al (1989) Science 244:362-364). Due to its genome structure and sequence homology, this virus was assigned as a new genus in the Flaviviridae family. Like the other members of the Flaviviridae, such as flaviviruses (e.g. yellow fever virus and Dengue virus types 14) and pestiviruses (e.g. bovine viral diarrhea virus, border disease virus, and classic swine fever virus) (Choo, Q-L et al (1989) Science 244:359-3; Miller, R. H. and R. H. Purcell (1990) Proc. Natl. Acad. Sci. USA 87:2057-2061), HCV is an enveloped virus containing a single strand RNA molecule of positive polarity. The HCV genome is approximately 9.6 kilobases (kb) with a long, highly conserved, noncapped 5′ nontranslated region (NTR) of approximately 340 bases which functions as an internal ribosome entry site (IRES) (Wang C Y et al ‘An RNA pseudoknot is an essential structural element of the internal ribosome entry site located within the hepatitis C virus 5′ noncoding region’ RNA-A Publication of the RNA Society. 1(5): 526-537, 1995 July). This element is followed by a region which encodes a single long open reading frame (ORF) encoding a polypeptide of −3000 amino acids comprising both the structural and nonstructural viral proteins.
Upon entry into the cytoplasm of the cell, this RNA is directly translated into a polypeptide of ˜3000 amino acids comprising both the structural and nonstructural viral proteins. This large polypeptide is subsequently processed into the individual structural and nonstructural proteins by a combination of host and virally-encoded proteinases (Rice, C. M. (1996) in B. N. Fields, D. M. Knipe and P. M. Howley (eds) Virology 2nd Edition, p 931-960; Raven Press, N.Y.). Following the termination codon at the end of the long ORF, there is a 3′ NTR which roughly consists of three regions: an ˜40 base region which is poorly conserved among various genotypes, a variable length poly(U)/polypyrimidine tract, and a highly conserved 98 base element also called the “3′ X-tail” (Kolykhalov, A. et al (1996) J. Virology 70:3363-3371; Tanaka, T. et al (1995) Biochem Biophys. Res. Commun. 215:744-749; Tanaka, T. et al (1996) J. Virology 70:3307-3312; Yamada, N. et al (1996) Virology 223:255-261). The 3′ NTR is predicted to form a stable secondary structure which is essential for HCV growth in chimps and is believed to function in the initiation and regulation of viral RNA replication.
The NS5B protein (591 amino acids, 65 kDa) of HCV (Behrens, S. E. et al (1996) EMBO J. 15:12-22), encodes an RNA-dependent RNA polymerase (RdRp) activity and contains canonical motifs present in other RNA viral polymerases. The NS5B protein is fairly well conserved both intra-typically (˜95-98% amino acid (aa) identity across 1b isolates) and inter-typically (˜85% aa identity between genotype 1a and 1b isolates). The essentiality of the HCV NS5B RdRp activity for the generation of infectious progeny virions has been formally proven in chimpanzees (A. A. Kolykhalov et al. (2000) Journal of Virology, 74(4), p. 2046-2051). Thus, inhibition of NS5B RdRp activity (inhibition of RNA replication) is predicted to cure HCV infection.
Based on the foregoing, there exists a significant need to identify synthetic or biological compounds for their ability to inhibit HCV.